This application is based on and claims the benefit of German Patent Application No. 201 00 911.0 filed Jan. 18, 2001, which is incorporated by reference herein.
The invention relates to a flexible electrical cable with a cable core made of a plurality of insulated conductors that are stranded together, and surrounded by at least one sheath.
Such flexible electrical cables are used, for instance, as elevator cables or as so-called drag chain cables. During operation of corresponding equipment, the cables are continually moved in special drag chains. The cables are either shielded or unshielded. The shielded version is used particularly to meet special electromagnetic compatibility requirements.
The complete energy and information supply of industrial equipment and machine tools has thus far been effected via drag cables that are individually installed in so-called drag chains.
In the past, the maximum chain length was 6 meters with motion rates of 180 m/min and general acceleration rates of 2 m/sec2. A technology with substantially improved drag chain construction, which is already practiced today in extreme applications, permits speeds of up to 500 m/min with motion lengths of up to 50 m and acceleration rates of 8 m/sec2 and more.
One solution, which is practiced to meet extreme requirements, consists of a flat cable construction with laterally arranged steel cables. Such a cable requires more space.
Another solution provides for the typical round construction of the cable, in which the sheath consists of a so-called steel/polyurethane composite construction. The drawback of this cable is the poor connection of the carrier element to the drag chain and the more difficult cable preparation and termination.
Under extremely difficult conditions, the known cables fail due to so-called corkscrew formation. This causes substantial downtime of the industrial equipment.
The object of the present invention is to provide a flexible electrical cable for extreme requirements, which is suitable for traversing distances of more than 30 meters at speeds of up to 500 m/min and acceleration or deceleration rates of up to 10 m/sec2. In addition, the cable is to be simple to prepare and terminate.
This object is attained by a flexible electrical cable with a cable core made of a plurality of insulated conductors that are stranded together, an inner sheath filling up the interstices between strands, a wrapping resting on the inner sheath, an armor braiding with an optical coverage of 30%-80% and a plastic outer sheath penetrating the interstices of the armor braiding.
Further advantageous embodiments of the invention will be clear from the detailed description below in conjunction with the appended claims.